Optical depth profiling of band gap engineered interfaces in amorphous silicon solar cells at monolayer resolution

Abstract

Real time spectroellipsometry and a two-layer optical analysis have been applied to obtain alloy composition (x) and optical gap (Eg) depth profiles with ∼3 Å resolution and sensitivities better than ±0.01 in x and ±0.02 eV in Eg for graded amorphous semiconductor alloy thin films prepared by plasma-enhanced chemical vapor deposition. Graded amorphous silicon–carbon alloy (a-Si1−xCx:H) layers incorporated at the i–p interfaces of a-Si:H n-i-p solar cells have been studied using these methods, and the layer characteristics have been related to improvements in solar cell performance.